Field of the Invention
The present invention relates to a substrate cleaning apparatus for cleaning a surface of a substrate such as a semiconductor wafer and drying the substrate, and more particularly to a substrate cleaning apparatus which can deal with a large semiconductor wafer having a diameter of 450 mm, and can clean a surface of a substrate efficiently after a polishing process such as CMP and dry the substrate.
Description of the Related Art
For example, in a damascene interconnect forming process for forming interconnects by filling a metal into interconnect trenches formed in an insulating film on a surface of a substrate, an extra metal on the surface of the substrate is polished away by chemical mechanical polishing (CMP) after the formation of damascene interconnects. A residue of a slurry (slurry residue) that has been used in polishing, metal polishing debris and the like exists on the surface of the substrate after polishing. Therefore, it is necessary to remove the residues (particles) remaining on the surface of the substrate after polishing.
As a substrate cleaning method for cleaning a surface of a substrate after polishing, there has been known a roll scrub cleaning method for cleaning a surface of a substrate, such as a semiconductor wafer, with a long cylindrical roll cleaning member (roll sponge or roll blush) extending horizontally by rotating the substrate and the roll cleaning member while keeping the roll cleaning member in contact with the surface of the substrate in the presence of a cleaning liquid. The substrate which has been cleaned is generally rinsed by pure water (DIW) or the like, and is then spin-dried by rotating the substrate at a high speed, as disclosed in Japanese laid-open patent publication No. 11-340184.
In a substrate cleaning apparatus for cleaning a substrate such as a semiconductor wafer in the presence of a cleaning liquid while the substrate is rotated, it is difficult to process (clean) an entire surface of the substrate uniformly because of different flow velocities of the cleaning liquid, different thicknesses of liquid films and different temperatures of the cleaning liquid at respective portions such as a central portion, an edge portion, and the like of the substrate surface. Further, in the case where the substrate surface having an exposed low-dielectric constant film (low-k film) serving as an insulating film is cleaned, because the low-k film is hydrophobic, non-uniformity of water wetting properties of the substrate surface is increased and uniform cleaning over the entire surface of the substrate becomes further difficult. Particularly, when a surface of a large substrate such as a semiconductor wafer having a diameter of 450 mm is cleaned, this tendency becomes prominent.
Recently, copper has been used as interconnect metal. When copper is brought into contact with a liquid such as pure water containing no anticorrosive, the copper becomes eroded easily by oxygen contained in the liquid such as pure water, resulting in reliability degradation in copper interconnects and a decrease in product yield due to short-circuit or open-circuit of the copper interconnects. Therefore, it is desirable that when the substrate surface having the exposed copper is cleaned, corrosion of copper caused by oxygen contained in the liquid such as pure water should be prevented as much as possible. Even if pure water or the like having a small amount of dissolved oxygen is used, corrosion of the copper surface caused by dissolution of oxygen in the air into pure water or the like may occur when the substrate surface is cleaned (rinsed) by supplying pure water or the like.
In order not to take oxygen in the air into pure water or the like which has no anticorrosive and is used for cleaning the substrate surface, it is considered that the substrate surface is cleaned in an inert gas atmosphere. However, in the substrate cleaning apparatus for cleaning the substrate such as a semiconductor wafer in the presence of the cleaning liquid while the substrate is rotated, it is necessary to install a mechanism for holding the substrate and rotating the substrate. Therefore, in the case where a cleaning unit having such mechanism is housed in a process chamber, the volume of the process chamber becomes considerably large. Thus, it is difficult to create a desired inert gas atmosphere in the process chamber.
As a substrate cleaning apparatus for cleaning a surface of a substrate without rotating the substrate, there have been proposed a substrate cleaning apparatus in which after polishing, a substrate is cleaned while the substrate is conveyed in one direction by a roller conveyer or the like as disclosed in Japanese laid-open patent publication Nos. 10-270392, 2002-217151 and 2006-73573, a substrate cleaning apparatus in which after polishing, a substrate is cleaned while the substrate is conveyed in non-contact state by a propulsive force of fluid jet as disclosed in Japanese laid-open patent publication No. 2005-322936, and a substrate cleaning apparatus in which after polishing, a substrate is cleaned while the substrate is conveyed by a transport belt as disclosed in Publication No. 2001-501030 for Published Japanese translation of PCT International Publication No. WO98/08418.
Further, there have been proposed a substrate cleaning apparatus for cleaning a surface of a substrate by ejecting mist-like fluid (fluid mixture of gas and liquid) from a two-fluid nozzle to the surface of the substrate during conveyance of the substrate as disclosed in Japanese laid-open patent publication Nos. 2006-247618 and 2010-118644, and a substrate cleaning apparatus for cleaning a surface of a substrate in a store room filled with an inert gas such as nitrogen gas in order to prevent oxidation or reforming of the processed surface of the substrate as disclosed in Japanese laid-open patent publication No. 2004-22940.
The applicant of the present invention has proposed a substrate processing apparatus having at least one of an ultrasonic cleaning apparatus for cleaning a surface of a substrate by ultrasonic waves propagated through a liquid and a two-fluid jet cleaning apparatus for cleaning the surface of the substrate by two-fluid jet comprising a fluid mixture of gas and liquid as disclosed in International Patent Publication No. WO 2007/108315.